For selection at SPA, Delhi marks are distributed in several criteria which are as follows.
In the interview, they usually ask the following questions.
School of Planning and Architecture, Bhopal is definitely the better option. In Architecture, SPAs are equivalent to IITs. Since SPAs are operated under the Ministry of HRD, they offer better infrastructure, funds, and facilities for students. The placement opportunities offered to the students are quite good too. Students get internships ranging from INR 10,000 to INR 60,000.
CCA is a reputed name in the field of Architecture, but it has limited exposure.
Rather than preparing to join SPA Delhi, you should prepare to be an Architect or Designer. Try to learn software such as sketch up, Revit, 3D max, etc. These are fun to learn. Also, make a habit of reading articles and publishings related to Architecture and Design. Practice sketching whatever you like.
For a UG course at SPA Delhi, you will need to go through JEE Main (Paper 2).
The choice of your institute depends on what you are expecting from it. For instance, if you are just after the brand name, then the IIT tag will come to your rescue. However, if you are on the lookout for quality education that will match your requirement to pursue a career in architecture, then SPA is a very good option. The only drawback is that there are no Institute placements and you need to have a good portfolio or Architectural background to get a good job.
If you are after placements, IIT Kharagpur and Roorkee can guarantee you very good packages, sometimes even in crores. The issue with this option is that you will have to first clear JEE Advanced and then AAT, after which only you can get admission.
I have told you the positive and negative implications of both the institute, make a wise decision.